This invention relates generally to equipment, thermal equipment and more particularly to high efficiency equipment for controlling heat and humidity as well as to take advantage of the heat capacity, density and flow of humid air. The structural embodiment of the invention is an improved single and double sided doorless humidity cabinet.
Thermal equipment, particularly thermal equipment in use in the food industry, will ideally require as precise a thermal and humidity control as possible. Because of the required ease of transport of food, most such equipment must have high user access, typically a rack of trays for quick removal for use in loading, bringing to temperature and maintaining temperature. Tray loading and storage usually requires a wide opening such as a door which provides a continual stream of upset to the internal environment. A unit of equipment needs to have the ability to adjust from a condition of intermittent and continual usage. The food items recently added should come to a good temperature and humidity condition quickly.
Complicating this goal is the physics associated with the inside of the unit of equipment. Where hot air sources and heating elements are present, there is a danger that the dry heat will harden the food, and that the moist heat will condense on the food to make the food soggy. These are the extreme limits of wrong operation. More common are the closer limits of wrong operation in that food on horizontal racks for example, in the upper reaches overheats and dries out, whereas food on the lower reaches experiences condensation and is too cool.
Physical and scientific limitations on a common space for environmental control are not only difficult to maintain, but monitoring in order that control may be effected is also problematic. Temperature probes without more don""t indicate moisture. One hundred eighty degrees of moist heat can cause heat and moisture penetration into food to bring the food to its final heated and moist condition more quickly. The same temperature of dry heat could cause hardening and spoilage of the food in a fraction of the time.
Application of heat is another problem. Where a pan is heated, no benefit is had unless it is certain that water is present, and unless it is certain that the humidity reaches the other areas of the cabinet. Where a dry heating element is energized, the amount of heat leaving the element before shut off depends upon the moisture, and therefore total heat capacity of the volume of air in the unit of equipment. Thus, temperature alone will not give an indication of how much thermal energy has been introduced. Humidity alone will not give an indication of how much thermal energy has been introduced, and neither will it enable a projection based upon usage of the equipment for quick additional moisture and thermal input.
Another problem with conventional equipment configuration is the vented cabinet. Where a vent is provided, the cabinet continuously emits a mixture of moisture and air representing losses in energy due to the raised temperature of the exiting components compared to ambient temperature, and the energy which must be added to to vaporize water to replace the humidity lost from the vent. Vented systems also have a physical limitation as to where they can be placed to insure that the vented exit does not cause condensation on other equipment or walls, and that the condensation exit is not blocked as it would upset the steady state temperature and moisture movements within the unit, and likely cause the food to become water laden or soggy.
The thermal environment equipment and process of the present invention is illustrated through structures and processes described with respect to a single and double sided ventless humidity cabinet, and which may also optionally be a doorless humidity cabinet especially if access occurs often enough such that operating a door would be an efficiency distraction, and is a working assembly made up of a number of component parts. The components for full illustration number sixteen, and include: cabinet box (housing), wet heating element(s) or wet heat source, water temperature probe, inlet valve, drain valve, level sensor(s), water, water level, Dry heating element(s) or dry heat source, upper temperature probe or upper humidity probe(s), middle temperature probe(s) or middle humidity probe(s), lower temperature probe(s) or lower humidity probe(s), air curtain fan(s) both to isolate the warm moist air inside from the dry cooler air outside, and to provide internal circulation to the internal environment more even, doorless entry window(s), arrows showing laminar air flow direction forming air curtain and then mixing steam with dry heat, and a special customizable wall that is normally only included in double sided unit.
The cabinet box for the ventless system is preferably made of a rigid material such as metal or plastic and should be capable of safely holding hot water and steam with minimum ambient thermal loss through the cabinet walls. The ventless steam cabinet shape most commonly is box shape; however, for design efficiency or visual savvy can be any shape or size as long as it can hold its humidity and perform the function of producing steamy humid environment for the products contained within. Ventless indicates that there is no deliberate vent for vapor and hot air, and that any escape of heated vapor air mixture is with the removal of food, or through leakage from the doorless opening, mitigated by the air door or air guarding flow at the service opening.
The inlet valve allows for the water to flow into the cabinet box and can be manually or electronically controlled. The level sensor(s) is a device or devices that establish when the correct water level, the optimum amount of water in the unit, has been reached. The level sensor is also a device that detects where the water is in the system. If the water level is too low or too high, it will detect it, take an action, and could also generate error signals for other problems with the water level. The level sensor can range from a simple float to a remote sonic, infrared, heat, electric, electronic, or other means of establishing the water level. The water is heated with the wet heating element(s) or wet heat source which can be water immersible electric heating elements, gas heat, microwave, electronic, light, or other kind of heat generating method or source. The water temperature probe detects the temperature of the water. The water temperature probe can be a simple thermistor to an infrared, electronic, or other means for attaining water temperature. The drain valve allows for the water to flow out of the cabinet box and can be manually or electronically controlled. The steam from the water in the cabinet box provides a portion of the heat and most of the humidity.
The dry heating element(s) or dry heat source which can be air electric heating elements, gas heat, microwave, electronic, or other kind of heat generating method or source and is used to dry out air and generate heat or dry hot air for the cabinet. The dry heating element(s) or dry heat source is most often placed at the top of the cabinet; however, this does not have to be the case and other methods of injecting dry heated air into the cabinet box could be used.
The upper temperature probe(s) or upper humidity probe(s), middle temperature probe(s) or middle humidity probe(s), and lower temperature probe(s) or lower humidity probe(s) detects the amount of humidity, dry heat, and temperature generated and how well the dry air and wet steam are mixing. The upper temperature probe(s) or upper humidity probe(s), middle temperature probe(s) or middle humidity probe(s), and lower temperature probe(s) or lower humidity probe(s) can be a simple thermistor, humidity sensor to an infrared, electronic, or other means for attaining humidity and temperature. The upper temperature probe(s) or upper humidity probe(s), middle temperature probe(s) or middle humidity probe(s), and lower temperature probe(s) or lower humidity probe(s) represent three general zones for measurement, although less or more may be utilized, the three being: lower, middle, and upper.
For Example, with a tall cabinet of over five feet, it may be desirable to utilize more zones. However, it would be possible to use one of the probe locations creating one zone instead of three for creating less cost and simplicity with a decrement in accuracy. This is especially true for smaller units of equipment. The reverse would also be true in having more probes placed inside the cabinet adding to the cost and greatly increasing accuracy. Some units of equipment are equipped with doorless entry window(s) are/is the window through which you can grab the products inside through without having to open a door. By not having a door to open speed of service is greatly increased, and a lesser perturbation on the conditions within the equipment are created.
On a single sided ventless humidity cabinet, the ventless entry window is typically only on one side of the line. On a double sided ventless humidity cabinet there are typically two doorless entry windows, one for each side so that workers can withdraw food on both sides of a serving line pulling from the cabinet at the same time. An optional door may be used where access will not occur for some time, and to more efficiently enable the internals of the cabinet to churn with air flow and better accomplish moisture and thermal mixing.
In the double sided ventless humidity cabinet there may preferably be a customizable wall in the cabinet box to prevent airflow from occurring into one side by its doorless entry window and out the other by its doorless entry window should they both be operated at the same time. The custom wall can include small holed areas and doors to move products from one side of the cabinet to the other with ease. In the majority of the cases you need a customizable wall in the cabinet box to prevent airflow in one side and out the other. However, it would be possible that in some locations which do not have large air movement and pressure differentials to operate with removal of the wall completely.